There's an issue opened about it: https://gitlab.com/relan/fennecbuild/-/work_items?show=eyJpaWQiOiIxNzYiLCJmdWxsX3BhdGgiOiJyZWxhbi9mZW5uZWNidWlsZCIsImlkIjoxODY5NDI0MzF9
I think they should pût the toggle back to enable / disable it.
You still can deactivate the specific notification channel.